Flat panel type display devices have been variously examined as image display devices to be replaced from the existing mainstream cathode ray tubes (CRTs). Such flat panel type display devices include liquid crystal display devices (LCDs), electroluminescence display devices (ELDs), and plasma display devices (PDPs: Plasma Displays). In particular, the plasma display devices are expected to be applied to domestic wall-hung televisions, public large-sized information terminal devices, and the like because of advantages in relatively easily obtaining large screens and wide viewing angles, enhancing the resistance against environmental factors such as temperature, magnetism, and vibration, prolonging the service life, and the like.
The plasma display device emits light by applying a voltage in discharge cells composed of discharge spaces filled with a discharge gas such as an inert gas, to generate ultraviolet rays due to glow discharge in the discharge gas, thereby exciting phosphor layers in the discharge cells with the ultraviolet rays. In this way, the individual discharge cells are driven on a principle similar to that of fluorescent lamps, and these discharge cells of the number of several hundreds of thousand are collected to form one display screen. The plasma display device is mainly classified into a direct current driven type (DC type) and an alternating current driven type (AC type) from the viewpoint of the type of applying a voltage to discharge cells. The DC type and AC type plasma display devices each have some drawback and advantage.
The AC type plasma display device is suitable for high definition because barrier ribs for partitioning individual discharge cells from each other within the display screen are sufficient to be formed into, for example, stripe shapes, and is also advantageous in that since surfaces of electrodes for discharge are covered with a dielectric layer, the electrodes are less worn, to thereby prolong the service life.
To improve the contrast of a display screen of a plasma display device, there is known a technique of coloring barrier ribs into black, as disclosed, for example, in Japanese Patent Laid-open Nos. 2001-155644 and Hei 11-7126.
As a result of examination of the present inventors, it has become apparent that the contrast cannot be sufficiently improved only by coloring barrier ribs into black. To solve such a problem, the present inventors have found that the contrast of a display screen of a plasma display device can be improved by providing a configuration that a barrier rib is composed of a vertical rib and a lateral rib, wherein the lateral rib is composed of two or more rows of lateral rib elements, and have previously filed the application based on such knowledge (see Japanese Patent Application No. 2001-245909).
The barrier rib structure having the lateral and vertical ribs, which is formed into a so-called waffle shape, however, has the following production problem: namely, the waffle shaped barrier ribs are disadvantageous in making it difficult to drop phosphor paste on the bottom of each space surrounded by the barrier ribs in the printing step, thereby tending to cause a variation in applied amount of the phosphor material.
In view of the foregoing, the present invention has been made, and an object of the present invention is to provide a plasma display device capable of enhancing the contrast of external light, facilitating printing performed by dropping phosphor paste on the bottom of each space surrounded by lattice-like barrier ribs, and reducing a variation in applied amount of the phosphor paste as much as possible.